When Franklin Roosevelt replaced Herbert Hoover in the White House, the country's economy was in shambles but its security was not threatened. No American forces were engaged in significant military conflict; America faced no threats. The U.S. was largely disarmed militarily and disengaged internationally.Yet within a decade, American territory had been attacked for the first time in 130 years, a massive rearmament program was underway, and the U.S. was fighting a desperate struggle that spanned the globe and ultimately cost the lives of nearly half a million American service members. The seeds of that global conflict, unimaginable in 1933 given the relative weakness of Germany and Japan, were planted in the first years of the Roosevelt administration as FDR focused on the American economy.

Obama's more conciliatory foreign policy gives me pause. I have little concern for the opinion of other nations, except as it limits our options in defending our homeland. Is it possible that we should try to improve strained relationships? Of course, but never at the expense of our own security.

What threats will our next president face? Kagan illuminates:

It is important to note here the distinction between an enemy and a threat. Threats are problems to be concerned about in the future; enemies are organizations trying to kill Americans right now. Al Qaeda and Iranian agents are both killing Americans on a regular basis and have proclaimed their determination to kill more. They are enemies, not threats, and they will confront the next president from day one.There are threats too, such as Pakistan's instability, combined with its inability and unwillingness to confront the al Qaeda safe havens on its territory. The growth of al Qaeda organizations in Algeria and Somalia poses another. Russian adventurism on the borders of states to which the U.S. has already given security guarantees is still another. The dangers of nuclear proliferation if the North Korean regime collapses -- or if it does not -- are still another.Lastly, the next president will almost certainly face Iran's arrival at the threshold of nuclear-weapons capability. This, combined with Iran's efforts to develop long-range (and ultimately intercontinental) ballistic missiles and its global terrorist networks, is a threat to America's allies and to Americans at home.

It's the last piece of the puzzle. Is it more important than the economy? I'm not sure, but it remains critical. Whoever gets the job, good luck to them, and us.